Structure for ultrasonic screening

ABSTRACT

Microparticle separation by ultrasonic screening in both batch and continuous operations and structure for accomplishing such operations. In the batch operation, particles to be cleaned and separated in accordance with their size are placed in a filter screen container, and the filter screen container is immersed in a water bath which is vibrated at an ultrasonic frequency so that the filter screen is maintained in a clean condition and the particles are scrubbed clean so as to pass readily through the filter screen under pressure. In the continuous microparticle separation operation, material is fed into a first chamber in which a vibrated water bath is maintained by water jets directed toward a vibrated filter screen separating a container into a first and second chamber. Filtered material and a portion of the water bath are withdrawn from the second chamber, and the rest of the water along with the residue of the material to be filtered are withdrawn from the first chamber. In both the batch and continuous methods, the water bath and/or filter medium are vibrated at between fifteen and sixty thousand hertz.

. 1 United States Patent [1 1 [111 3,782,547 Dietert 1 Jan. 1, 19 74[54] STRUCTURE FOR ULTRASONIC 6,707,502 12/1968 Netherlands 210/19SCREENING 1 Primary Examiner-Robert Halper [75] inventor, Harry W.Dletert, Kerrv1lle, Tex. Att0mey Dale R. Small et aL 1 v [73] Assignee:Barry W. Dietert Co., Detroit,

Mich. [57] ABSTRACT [22] Filed; Oct 2 1971 Microparticle separation byultrasonic screening in I both batch and continuous operationsandstructure PP 188, 51 for accomplishing such operations. In the batchopera I tion, particles to be cleaned and separated in accor- 52 us. c1209/268, 209/1, 210/19 dance with their Size are Placed in a filterScreen 9911- 51 Int. c1. B03b 3/00, B07b 1/00 1 miner, and the filterScreen ntainet is immersed in a [58] Field of Search 209/269, 1, 268,water bath which vibrated at an ultrasonic 209 2 3; 2 0 59 R quency sothat the filter screenis maintained in a clean condition and theparticles are scrubbed clean [5 R f s Cited so as to pass readilythrough the/filter screen under UNITED STATES PATENTS pressure. In thecontinuous microparticle separation 2 468 5 50 4/1949 F nth I v 210m) Xoperation, material is fed into a first chamber in which 2'800228 7/1957209,269 a vibrated water bath is maintained by water jets 3:463:321 I8/1969 Va 2;: X directed toward avibrated filter screen separating a3,490,584 1/1970 Balamuth.... .1209/1 Container into a first and Secondchamber- Filtered 3,009,576 1 1/1961 Jones 209/268 material and aportion of the water bath are withdrawn 1 3,064,806 H1 2 Hukki 209/2 Xfrom the second chamber, and the rest of the water 314101532 1 11/1968304m 259/1 R X along with the residue of the material to be filtered3490585 1 11/ 209/270 X are withdrawn from the first chamber. In boththe 3,720,306 3/1973 Hedler 209 b t h d ti uo e s the water and/OrFOREIGN PATENTS OR APPLICATIONS filter medium are vibratedat betweenfifteen and 886,884 10/1951 Germany 210/19 Sixty thousand heril- I iTen-tin 3 iii awing fihre s ALTERNATING 1 POWER VIBRATOR 24 SOURCE p lPATENTEUJAN H974 3,782,547

IO i

ALTERNATlNG I H "Q15 POWER 1 VIBRATOR 24 SOURCE FIG.2

ALTERNATING POWER SOURCE FIG.3

INVENTOR. HARRY W. DIETERT STRUCTURE FOR ULTRASONIC SCREENING BACKGROUNDOF THE INVENTION 1. Field of the Invention The invention relates tomicroparticle separation and refers more specifically to the filteringof particles of, for example, up to fifty microns in size through afilter screen with the particles in a liquid bath by vibrating theliquid bath and/or filter screen at an ultrasonic frequency to scrub theparticles and maintain them and the filter screen clean and to thereforemaintain the filter screen at maximum efficiency at all times.

2. Description of the Prior Art Microparticle separation such as theseparation of foundry sand grains and foundry sand additives has oftenbeen accomplished by the use of fine filter means. The particles to beseparated by filter means often have coatings of air, clay or othermaterial thereon which prevent their ready passage through a filtermedium of for example a fifty micron screen.

In addition, the filter mediums of the past have become clogged witheither coated particles or particles too large to pass therethrough at arelatively rapid rate whereby the filtering capabilities of the filtershave been greatly diminished ina relatively short time, requiringstopping of the separation process and cleaning of the filters. 7

Cleaning by causing ultrasonic vibrations in a liquid bath has beenknown in the past, as for example in U. S. Pat. Nos. 3,305,581 and3,463,321. However, such cleaning has not been in disclosed herein.

SUMMARY OF THE INVENTION A sample of particulate material as, forexample, foundry sand may be separated in accordance with the particlesize thereof in either a batch or a continuous operation in accordancewith the present invention.

In the batch operation, the particles to be separated may be placed in afilter screen container and the filter screen container placed in awater bath in an outer container. The outer container includes a drainfor the water bath adjacent the top thereof, while the water bath isplaced within the filter screen container to maintain a pressure headbetween the water bath inside and outside of the filter screen containerand the water bath and/or filter screen are vibrated at an ultrasonicfrequency.

In the continuous operation, the particles to be separated are passedinto a first chamber in a container into which a water bath isintroduced in a manner to force the particles toward a filter screenseparating the first chamber from a second chamber of the container,while the water bath and/or filter screen are again vibrated at anultrasonic frequency. A portion of the water bath is withdrawn togetherwith the filtered parti' cles from the second chamber of the container,while the remainder of the water bath is withdrawn from the firstchamber along with particles too large to pass through the filterscreen.

In both the batch and continuous microparticle separation operations,the vibration is at ultrasonic frequen' cies of between fifteen andsixty thousand hertz, a pressure head is maintained across the filtermedium by the introduction of the water into the water bath, andadditives are added to the water bath as desired to wet andlor dispersethe particles therein.

conjunction with filtering as BRIEF DESCRIPTION OF THE DRAWINGS.

FIG. 1 is a longitudinal section view of ultrasonic screening structurefor batch-type microparticle separation constructed in accordance withthe invention and taken substantially on the line 1-1 in FIG. 2.

FIG. 2 is a transverse section view of the ultrasonic screeningstructure illustrated in FIG. 1 taken substantially on the line 2-2 inFIG. 1.

FIG. 3 is a longitudinal section view of a modification of theultrasonic screening structure illustrated in FIG. 1 for continuousmicroparticle separation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ultrasonic screeningstructure 10 for microparticle separation as shown in FIG. 1 includes anouter container 12, an inner filter container 14, a source of ultrasonicalternating electrical energy of between fifteen and sixty thousandhertz 16 and an electrical frequency to mechanical vibration transducer18. The microparticle separation structure 10 further includes the means21 for providing a water bath 20 in the containers 12 and 14 and means22 for placing additives in the containers l2 and 14.

The container 12 is substantially square and has a closed bottom end 24and an open top end 26. The bottom 24 is relatively thin and is highlypolished so as to transmit ultrasonic vibrations from the transducer 18to the water bath 20in the containers l2 and 14. An overflow outlet ordrain 30 is provided in the container 12 adjacent the open end 26thereof.

The filter container I4 is constructed of a fine mesh screen such astwenty microns having suitable supporting structure. The filtercontainer 14 is separated from the bottom 24 of the container 12 bysuitable means such as the recessed bottom 32 of the filter containerconstruction and/or the cross-shaped spacing member 34 on which thecontainer 14 is positioned in the container l2.

The source of alternating electrical energy 16 and the electrical toultrasonic vibration transducer 18 are known in the art and will nottherefore be considered in detail herein. Such equipment is, forexample, ob tainable from the Branson Instruments Company, a subsidiaryof Smith Kline & French Laboratories, Stamford, Connecticut.

The structure 21 for maintaining a fluid bath in the containers 12 and14, as shown in FIG. 1, may be a water conduit 36 having a valve 38therein for regulating the water supply to the containers. A rubber tube40 or the like is placed over the end 42 of the conduit 36 to preventinjury to the fine mesh screen container 14 in use. The structure 22 foradding additives to the water bath 28 may be entirely similar to thestructure 21.

In operation of the microparticle separation structure illustrated inFIGS. 1 and 2, a batch of material to be separated in accordance withthe size of the particles therein is placed in the filter container 14and the container 14 is positioned within the outer container 12, asshown in FIG. 1. A water bath is provided in the containers 12 and 14through the conduit 36 and the water bath 28 is vibrated at anultrasonic frequency by the transducer 18 in response to the ultrasonicsignal from the source of ultrasonic alternating electrical energy 16.

Both the particles 44 to be separated in the water bath 28 and thefilter container 14 are thus vibrated at an ultrasonic frequency wherebythe particles scrub each other and the filter so that the particles arefreed from air bubbles and extraneous material such as clay or otherfine material which may coat them and air bubbles and lodged particlestoo large to pass through the filter are removed from the filter 14 Apressure head may be maintained between the inside and outside of thefilter container 14 by regulating the valve 38 in conjunction with theopening of the overflow 30 from the outer container 12. Thus, theparticles are urged to pass through the filter screen 32.

In addition, due to the additives passed through the additive addingmeans 22 into the water bath 28 such as, for example, sodiumpyrophosphate and sodium hydroxide, the particles may be wetted and/ordispersed in the water bath 28 which also aids their filtering throughthe filter 14.

After a predetermined time of filtering the particles 44 as indicatedabove, the filter container 14 is removed from the outer container 12and the filter container is weighed. The difference in weight betweenthe initial weight of the filter container having the particles to beseparated therein and the weight after filtering will provide anaccurate indication of the quantity of material filtered through thefilter container 14, if such measurement is desirable.

Alternatively or in addition, the overflow fluid from the overflownozzle 30 may be dried and weighed to determine the amount ofparticulate material passing through the filter screen 14. Thus, anaccurate indication of the quantity ofa material having less than apredetermined size may be determined by means of the structureillustrated in FIG. 1 and the batch method described.

Should the continuous separation of fine material from coatingand largermaterial be desired, the structure 46 illustrated best in FIG. 3 isprovided. The structure illustrated in FIG. 3 includes a container 48having a first chamber 50 and a, second chamber 52 therein with a filtermember 54 such as a twenty micron filter screen separating the chambers50 and 52.

The water bath 56 in the container 53 which is maintained by jets 58opening into chamber 50 from supply conduit 60 along with the filterscreen 54 is again vibrated at ultrasonic frequencies of between fifteenand sixty thousand hertz by the transducers 62 excited by an alternatingelectric signal from the source 64. Particulate material which may becarried by the water bath is introduced into chamber 50 through conduit66. Filtered particles and a portion of the water bath are withdrawnfrom the chamber 52 through conduit 68,

while the remainder of the water bath is withdrawn through the conduit70 from the chamber 50.

In operation of the continuous ultrasonic screening structure 14 formicroparticle separation in a water bath, the water bath in the chambers50 and 52 is vibrated at the ultrasonic frequency by the transducers 62.Again, the particles 70 are caused to scrub each other and pass throughthe filter screen 54 which is maintained in a clean condition due to thevibration thereof with the water bath and a hydrostatic head is providedbetween the chambers 50 and 52 due to regulation of the inlet pressurein the conduits 60 and 66 and the outlet pressures in the conduits 68and 70.

The particles as they pass into the chamber 50 through the conduit 66are urged toward the filter screen 54 by means of the water jets 58 andthe baffles 72 directing the water jets and thus the particles towardthe screen 54. The particles which pass the screen 54 and into chamber56 are-removed through conduit 68. Those that do not pass through screen54 pass out of chamber 50 through conduit 70.,

Again, if it is desired to provide an absolute indication of thequantity of particles passing the screen 54 or the material not passingthe screen 54, or the relative percentage thereof, the material may beseparated from the water bath withdrawn from the conduits 68 and 70,dried and weighed to provide a basis for any mathematical calculation.

While one embodiment of the invention has been considered in detailtogether with a modification thereof, it will be understood that otherembodiments and modifications are contemplated. Thus, the inventor doesnot wish to be limited to the separation of foundry sand particles or tothe use of the structure and method for microparticle separation byultrasonic screening in foundry applications. It is therefore theintention to include all methods and structures as suggest themselvesfrom the above disclosure within the scope of the appended claims.

What I claim as my invention is:

1. Structure for microparticle separation by ultrasonic screening undera pressure head in a batch operation comprising a first and a secondwater bath chamber defined by an outer container and a microparticlescreen inner container positioned within the outer container having abottom which is spaced from the bottom of the outer container with theinner container positioned within the outer container, a cross shapedmember positioned on the bottom of the outer container on which theinner container is positioned to facilitate circulation of the waterbath through the bottom of the inner container, means for producing awater bath flowing from the first of the chambers into the secondchamber through the screen and out of the second chamber continuously,means for maintaining a pressure head in the first chamber duringmicroparticle separation and means for vibrating the water bath at anultrasonic frequency including a source of alternating electrical power,a vibrator connected to the source of electrical power for actuationthereby and connected to the bottom of the outer container to produceultrasonic vibration thereof on actuation whereby a portion of themicroparticles to be separated placed in the water bath in the onechamber all of which are of a size to pass through the screen are movedwith the flow of the water bath through the screen and into the secondchamber, and means for discharging the water bath and portion of themicroparticles from the structure for microparticle separation includingan overflow nozzle positioned adjacent the top of the outer container. I

2. Structure for microparticle separation by ultrasonic screening undera pressure head in a continuous operation comprising a first water bathchamber for continually receiving microparticles placed therein and asecond water bath chamber which chambers are formed by a containerseparated by a screen, means for producing a water bath flowing from thefirst of the chambers into the second chamber through the screen and outof the second chamber continuously, means for maintaining a pressurehead in the first chamber during microparticle separation comprisingwater jets extending into the bottom of the first chamber, deflectionmeans in the first chamber for deflecting the microparticles placedtherein toward the screen in conjunction with the water jets, means forvibrating the water bath at an ultrasonic frequency comprising a sourceof alternating electrical power, vibrators positioned in the surface ofthe container parallel to the screen in contact with the water bathconnected to the power source for providing vibrations at ultrasonicfrequency on actuation whereby a portion of the microparticles to besepachamber.

1. Structure for microparticle separation by ultrasonic screening undera pressure head in a batch operation comprising a first and a secondwater bath chamber defined by an outer container and a microparticlescreen inner container positioned within the outer container having abottom which is spaced from the bottom of the outer container with theinner container positioned within the outer container, a cross shapedmember positioned on the bottom of the outer container on which theinner container is positioned to facilitate circulation of the waterbath through the bottom of the inner container, means for producing awater bath flowing from the first of the chambers into the secondchamber through the screen and out of the second chamber continuously,means for maintaining a pressure head in the first chamber duringmicroparticle separation and means for vibrating the water bath at anultrasonic frequency including a source of alternating electrical power,a vibrator connected to the source of electrical power for actuationthereby and connected to the bottom of the outer container to produceultrasonic vibration thereof on actuation whereby a portion of themicroparticles to be separated placed in the water bath in the onechamber all of which are of a size to pass through the screen are movedwith the flow of the water bath through the screen and into the secondchamber, and means for discharging the water bath and portion of themicroparticles from the structure for microparticle separation includingan overflow nozzle positioned adjacent the top of the outer container.2. Structure for microparticle separation by ultrasonic screening undera pressure head in a continuous operation comprising a first water bathchamber for continually receiving microparticles placed therein and asecond water bath chamber which chambers are formed by a containerseparated by a screen, means for producing a water bath flowing from thefirst of the chambers into the second chamber through the screen and outof the second chamber continuously, means for maintaining a pressurehead in the first chamber during microparticle separation comprisingwater jets extending into the bottom of the first chamber, deflectionmeans in the first chamber for deflecting the microparticles placedtherein toward the screen in conjunction with the water jets, means forvibrating the water bath at an ultrasonic frequency comprising a sourceof alternating electrical power, vibrators positioned in the surface ofthe container parallel to the screen in contact with the water bathconnected to the power source for providing vibrations at ultrasonicfrequency on actuation whereby a portion of the microparticles to beseparated placed in the water bath all of a size to pass through thescreen are moved with the flow of the water bath through the screen andinto the second chamber, and means for discharging the water bath andportion of the microparticles from the structure for microparticleseparation including a drain for withdrawing part of the water bath fromthe first chamber and a drain for withdrawing the remainder of the waterbath and the portion of the microparticles from the second chamber.